Crowds gathered in George Square as police separated rival supporters of the union and independence.

Earlier in the evening, hundreds of people had crowded into the square, with union supporters and rivals sporting Yes badges arguing over the referendum result, while a chorus of Rule Britannia was countered by the Scottish anthem, Flower of Scotland.

While social media reports indicated that trouble continued into the early hours of the morning, a Police Scotland spokesman said groups had dwindled to sets of two and three people by around 1am.

He said: "Six people have been arrested so far in relation to the incident in George Square. Retrospective inquiries will be carried out which may lead to further arrests."

A Police Scotland spokesman said: "Officers are still investigating the cause."

Jonathan Coates, assistant sports editor at the Herald newspaper, posted a picture of the blaze on Twitter.

It was understood to be at the rear of the Herald office, but Mr Coates warned people speculating on the cause of the fire not to assume it was started by vandals targeting the paper for coming out in favour of Scottish independence.

"Don't jump to conclusions based on the picture I tweeted: no reason to suspect The Herald Group targeted by these vandals," he tweeted.